Variability of the tdh-related hemolysin (trh) gene of Vibrio parahaemolyticus of Pacific Northwest isolates: implications for detection and potential virulence of trh+ strains.
Presentation Abstract
Vibrio parahaemolyticus (Vp) is the most common cause of illness related to the consumption of raw or undercooked seafood. Globally, the O3:K6 serotype comprises the majority of clinical strains and is often referenced as a “pandemic complex.” Strains belonging to this complex encode the thermostable direct hemolysin (tdh), which is widely considered a reliable virulence marker. In the Pacific Northwest (PNW), the pandemic complex is abundant in the estuarine environment; however, no clinical cases have been associated the O3:K6 serotype in this region. Clinical cases in the PNW are largely associated with the geographically isolated O4:K12 serotype, which carries the similar but phylogenetically distinct tdh-related hemolysin (trh). We have recently shown that trh may be a more accurate marker of virulence in the PNW. Further, recent O4:K12 outbreaks in New York and Spain suggest that trh could become a globally important marker for virulence. Unfortunately, sequence variability in the trh gene is an obstacle to the development of reliable detection methods. Therefore, to identify suitable conserved regions for primer development, we evaluated trh sequence variability in over 50 trh+ Vp isolates. Preliminary results show the trh gene exhibits significant interstrain variation and is likely too variable for accurate detection. We propose the less variable urease R gene (ureR), which is genetically linked to trh, could serve as a useful proxy for the detection of trh+ strains. Current efforts are focused on the validation of ureR as a marker of virulent strains. Additionally, we are conducting an evolutionary analysis of the trh gene to identify the mechanisms responsible for the observed sequence variability. We hypothesize that the recent positive selection is shaping the evolution of this gene and we discuss how key nonsynonymous mutations may affect TRH functionality.
Session Title
Session S-08A: Harmful Algal Blooms, Climate, Shellfish, and Public Health - Emerging Issues in a Changing World
Conference Track
Harmful Algal Blooms and Shellfish
Conference Name
Salish Sea Ecosystem Conference (2014 : Seattle, Wash.)
Document Type
Event
Start Date
1-5-2014 5:00 PM
End Date
1-5-2014 6:30 PM
Location
Room 6C
Genre/Form
conference proceedings; presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Vibrio parahaemolyticus--Detection--Northwest, Pacific; Vibrio parahaemolyticus--Genetic aspects; Pathogenic microorganisms--Detection--Northwest, Pacific
Geographic Coverage
Salish Sea (B.C. and Wash.); Northwest, Pacific
Rights
This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.
Type
Text
Language
English
Format
application/pdf
Variability of the tdh-related hemolysin (trh) gene of Vibrio parahaemolyticus of Pacific Northwest isolates: implications for detection and potential virulence of trh+ strains.
Room 6C
Vibrio parahaemolyticus (Vp) is the most common cause of illness related to the consumption of raw or undercooked seafood. Globally, the O3:K6 serotype comprises the majority of clinical strains and is often referenced as a “pandemic complex.” Strains belonging to this complex encode the thermostable direct hemolysin (tdh), which is widely considered a reliable virulence marker. In the Pacific Northwest (PNW), the pandemic complex is abundant in the estuarine environment; however, no clinical cases have been associated the O3:K6 serotype in this region. Clinical cases in the PNW are largely associated with the geographically isolated O4:K12 serotype, which carries the similar but phylogenetically distinct tdh-related hemolysin (trh). We have recently shown that trh may be a more accurate marker of virulence in the PNW. Further, recent O4:K12 outbreaks in New York and Spain suggest that trh could become a globally important marker for virulence. Unfortunately, sequence variability in the trh gene is an obstacle to the development of reliable detection methods. Therefore, to identify suitable conserved regions for primer development, we evaluated trh sequence variability in over 50 trh+ Vp isolates. Preliminary results show the trh gene exhibits significant interstrain variation and is likely too variable for accurate detection. We propose the less variable urease R gene (ureR), which is genetically linked to trh, could serve as a useful proxy for the detection of trh+ strains. Current efforts are focused on the validation of ureR as a marker of virulent strains. Additionally, we are conducting an evolutionary analysis of the trh gene to identify the mechanisms responsible for the observed sequence variability. We hypothesize that the recent positive selection is shaping the evolution of this gene and we discuss how key nonsynonymous mutations may affect TRH functionality.
